Abstract 544: Increase in Isoflurane-mediated Blood-brain-barrier (bbb) Permeability is Regulated by Mmp3 via the Erk Signal Pathway

Introduction: The blood-brain barrier (BBB) normally maintains the CNS microenvironment. The effect of isoflurane, widely used in clinical anesthesia, on the BBB permeability has not been well studied. Matrix metalloproteinase 3 (MMP3) is implicated in the disruption of BBB. However, the direct role for MMP3 in regulating BBB and the underlying molecular mechanism has not yet been elucidated. We hypothesized that MMP3 plays a critical role in isoflurane mediated increase in BBB permeability. Methods: We used MMP3 deficient (MMP3 -/- ) mice and its littermate, wild-type (MMP3 +/+ ), as a control. Animals were assigned to either vehicle-air or isoflurane in 3 different groups: control, MMP3 -/- and control+MMP3 administration. We evaluated the anesthetic effect of isoflurane by the time of anesthesia induction, emergency time and volume of isoflurane. MMP3 levels were measured in different organs. We monitored the permeability of mouse BBB through in vivo (Evans blue dye extravasation, Sodium-FITC, and brain water content) and an in vitro model of BBB (Electrical cell impedance sensor assay and transwell permeability assay). To determine the mechanism of MMP3 on BBB permeability, we also used an ERK-inhibitor. Expression of the endothelial tight junctional protein was detected by both western blot and immunofluorescence staining. Results: The use of MMP3 increased the anesthetic sensitivity of isoflurane compared with the control group. In contrast, MMP3 KO mice displayed significantly longer induction time, higher isoflurane usage volume, and lower emergency time. Data showed that MMP3 increased BBB permeability in both in vivo and in vitro experiments, which is associated with a reduction in occluding, ZO-1 and claudin-5. We found mmp3 levels had negative correlations with tight junctional proteins and positive associations with p-ERK. Moreover, the use of an ERK-inhibitor abolished the effect of MMP3 on the junctional protein and in vitro BBB permeability. Conclusion: Our data suggest that MMP3 is required for modulation of isoflurane mediated BBB permeability by the reduction of tight junctional protein expression via the ERK pathway. Thus, mmp3 enhances the anesthetic effect of isoflurane, while the deletion of MMP3 protects against BBB disruption.